Air-speed acceleration recorder



Dec. 13; 1938. J 5, RED ET AL AIR-SPEED ACCELERATION RECORDER FiledApril 14, 1932 3 Sheets-Sheet 1 HENRY d. E. REID RICHARD v. RHODEINVENTORS I BY j ATTORNEY Dec. 13, 1938. J, 5 ET AL 2,139,694

AIR-SPEED ACCELERATION RECORDER Filed April 14,1932 :5 Sheets-Sheet 3 75W85 7m //////////////////////////fl 27 err 26 24 w 2 2 17.; Z115: 79 Q Io 72 :4

38 Z I5 z 4 Y HENRY a. E Far/0 RlCHA rw v. RHQDE F 6 INVENTORS ATTORNEYI Patented Dec. 13, 1938 UNITED) STATES 2,139,694 AIR-SPEED ACCELERATIONanoommn HcnryJ. E- Reid and Richard V. Rhoda, Hampton, Va. 1

Application April 14, 1932, Serial No. 605,324

11 Claims.

(Granted under the act of March 3, 1883, as

. amended April 30, 1928; 370 0.

Our invention relates broadly to an air-speed acceleration recorder andmore particularly to a devicefor use in an aircraft to indicateacceleration with respect to dynamic pressure.

The primary object of our invention is to provide an aircraft with aninstrument to enable the study of thecritical loading imposed on theaircraft in actual service i. e. during a period when the aircraft is inflight.

Another object of our invention is to provide an aircraft with aninstrument to record the relative severity with which different pilotsmaneuver their aircraft and thereby obtain a comparative check upon thefitness of pilots for diiferent classes of i5 flying.

A further object of our invention is to provide an instrument to recordthe magnitudes of acceleration obtained in transport aircraft with aview of determining which pilots or aircraft, or both,

20 are likely to cause the least irregular acceleration, and hence,ultimately, to provide the smoothest possible service.

-Still another object of our invention resides in providing aninstrument to determine the corre- 25 spending value of acceleration orload factor and lift coemcient encountered in flight of an aircraft.

A further object of our invention is in providing an aircraft with aninstrument for the purpose of studying the eifect of weather conditionsand terrain on general flying in'difierent sections of the countryespecially as to the effects of loads imposed on the aircraft.

With the above and other objects in view the in- 35 vention consists inthe construction, combination and arrangement of parts as will bedescribed more fully hereinafter.

Reference is to be had to the accompanying drawings forming a part ofthis specification,'1n 40 wh ch like reference .characters indicatecorresponding parts throughout the several views, and in which:

Figure l is a plan view of our instrument. 3 Figure 2 is a view on line2-2 of Figures 1 and Figure 3 is a plan view the cover removed. 3 Figure4 is a view on line 4--4 of Figures 1 and of our instrument with 50Figure 5 is a diagrammatical view of a form of our instrument.

Figure 6 is a view on line 6-6 of Figure 5. Figure 7 is a view of adetail .of the cover plate or cap of our instrumentr 5 Fig. 8 is a viewonline 8-8 of Fig. 4.

Referring more particularly to the drawings, l0 indicates a casinghaving a cover I I secured there to by screws l2. The casing with coverattached is air tight and has suitably mounted therein an accelerometerunit and a dynamic pressure unit, 5 both of which are connected to astylus or pen l3 for recording their movements on a chart.

The accelerometer unit consists of a weight I4 afiixed to a lever I5that has a hub end It pivoted for rotation to a post l9 secured in 8.lug in- 10 tegral with casing Ill. The lever l5, which is onset as at 2|with a forked end 22, is constrained by springs 23 that have one endsecured to' clips 24 and the other end looped through apertures 25 inthe forked end 22. The clips 24 are adjustably 16 secured by means ofwashers 80 on screws 26 that are placed through slots 21 in the clipsand extend into lugs 28 of the casing.

A lever 29 is pivoted by hub 30 on a post 3| secured in lug 32 on theopposite side of the casing 20 from lug 2d. The lever 29 (Figs. 3 and 4)is providedwith pin 33 that extends through a slot 34 of the forked end22 of lever l5. Movement of the lever l5 therefore, is transmitted tolever 29 which is rotatably fixed by screw 35 and washer 86 to 25 stylusarm 31 with stylus l3 secured thereto.

The dynamic pressure unit comprises a suitable flexible pressure cell ordiaphragm 88 having a bearing bracket 39 in the center thereof foroperating through a lever arm 40 of a bell crank a 30 multiplyingmechanism which is also connected by linkage to stylus arm 31. The bellcrank in addition to arm 40 consists of a shaft 4| rotatably pivoted byscrews 42 between two posts 43 and a lever arm 44 extending up fromshaft 4|. The le- 35 ver 44 passes through an aperture in lug 45 in oneside of a sector gear 46 that is secured for rotation to a shaft 41positioned between an upper plate 48 and a lower plate 49 attached bymeans of posts 5!! and pins 5| to plate 48. The upper plate 48 is 0mounted by screws 52 to posts 53 which are threaded into plate 54supported on collar 55 of a passage 55 to the diaphragm 38. Meshing withgear 46 is a pinion gear 51 mounted on shaft 58 positioned betweenplates 48 and 49. A coil hair 45 spring 59 which has one end fixed toshaft 58 and the other end to one of the posts 50 retains themultiplying mechanism in a neutral position through the pinion 51 andsector gear 46. An arm 60 riveted to and extending out from gear 48 is50 rotatably secured to a link 6 I that in turn is connected with stylusarm 31. Thus, movement of diaphragm 38 will be transmitted throughbracket 39 to lever arm 40 so as to rotate shaft 4| which rotation inturn moves by lever arm 44 the sector gear 46 and this movement of thesector gear 46 is then transmitted through arm 60 and link 6| to thestylus arm 31 which in turn moves stylus l3.

Cut into cover II is a suitable opening 62 into which is inserted andheld in place by a cap 63, a smoked glass 64 on which movements of thestylus l3 can be recorded. It will be noted that the accelerometer andpressure units are so constructed that respective movements thereof willcause stylus l3 to move across the glass 64 in directions substantiallytransverse to each other.

The cap 63 has an extending head 65 into which is cut a groove 66 toreceive a bail G'Iadapted to hold the cap firmly in place. The bail 61is fastened to cover H by eye bolts 68 having threaded shanks 69extending through and secured on the underside of. cover H by washers land nuts H.

The casing 10 is provided with passage 56 into which is threaded apressure tube 12 for supplying the full impact of air into the diaphragmTo transmit to the casing Hi the static pressure of air, a static tube13 is threaded into aperture 14 in the casing. For securing theinstrument to a panel board, threaded holes 15 adapted to receive boltsare suitably drilled into various parts of the casing.

Movement of stylus l3 by the accelerometer unit is regulated by dampingmeans consisting of a knurled screw I6 threaded through an aperture inthe cover and having its end bear against a friction plate 11 that hasone end riveted to the underside of the cover and the other end forkedas at 18 so as to fit around post 3| and set up the desired friction onthe hub end 30 of lever 29.

This friction may be adjusted to any desired value by screw 16 and inthe practical use of the instrument is set so that no movement of stylusi3 is obtained when the engines are idling or the craft is in steadyflight.

The instrument is so designed that, in practical use, it may beinstalled in an aircraft for any period of time. The readings will show,as desired, either the maximum and minimum accelerations at all airspeeds at which the aircraft has beemoperated during a period of serviceor the relations between acceleration and air speed for a singlemaneuver.

Our improved instrument may be used in such a manner that it will recordthe component of acceleration in any direction. When mounted so thatthis direction is perpendicular, to the wing chord, the accelerationrecorded in terms of g is a direct measure of applied load factor. Thelift coefficient corresponding to any acceleration is obtained throughthe use of the following formula:

in which a is acceleration, g is the acceleration of gravity, n is theload factor, Fa is the component of force on the aircraft normal to wingchord, W is the weight of the aircraft, CN is the normal forcecoefficient, r is the density of the air, V is the velocity and S is thewing area. n can be determined directly from the record of theinstrument, that is. from the recorded acceleration. V r V is thedynamic pressure measured by the instrument. The weight W and the wingarea S are known from the characteristics of the aircraft, which allowsthe determination of CN, the normal force coefficient.

For the purpose of describing the practical operation of our device, wehave diagrammatically stylus 13'.

shown in Figure a simplified form of our improved instrument wherein thediaphragm I! is connected to the stylus arm 31' through arm 19, lever 8|and link 82 whereby the movement of the diaphragm will be transmitted tothe The impact pressures are conveyed to the diaphragm 38 by tube 12which in turn is connected to a suitable entrapping device, such as theimpact side of a Pitot-static tube, not shown. The impact pressures willcause the diaphragm to expand but, in order to only record the dynamicpressures, the static pressure from the static side of the entrappingdevice, the Pitot-static tube, is brought to the inside of casing H) bytube 13. Thus, the expansion-of the diaphragm through the resultantdynamic pressures causes the arm 19, lever 8!, link 82 and stylus arm31' to move stylus It in a substantially horizontal direction in Fig. 5on the recording chart.

The chart 90 shown in this figure has one end mounted on a spindle 63and the other end fixed to a shaft 84 that can be rotated on the outsideof the casing by turning the head 85. This chart 90 is of a flexiblematerial, such as paper or any other material on which recording can bemade, so that the same can be conveniently rolled from the spindle 83onto the shaft 8|. In this mannervarious maneuvers can be separatelyrecorded.

When the aircraft is accelerated, weight M lags I in the oppositedirection to the sudden change of velocity and will eventually cause thelever arm l5 to move. This movement actuates through link 33 (which linkserves the same purpose as pin 33 and slot 34 of Figs. 3 and 4) andlever 29', stylus arm 31 causing the stylus l3 to move in thesubstantially vertical direction and record on the chart the relativeamounts of movements made by weight M and lever i5, thereby giving arecord of the acceleration made by the aircraft. In order to set up adefinite value for the amount of acceleration, the weight l4, linki I3and springs 23 can be adjusted to give the proper travel of the stylus[3' on the chart, and to prevent movement of the stylus when the engineor engines of the aircraft are idling while the aircraft is on theground or when the aircraft is in steady flight, the proper amount offriction is put on lever 29 by adjusting friction plate H (Fig. 6) byscrew 16'.

The herein described invention may be manufactured by or for theGovernment of the United States for governmental purposes without thepayment to us of any royalties thereon or therefor.

What we claim is: V

1. An instrument for an aircraft comprising a chart, a stylus andactuating means responsive to accelerations of the aircraft for movingsaid stylus in one direction substantially proportional to the appliedacceleration, and means responsive to dynamic pressures for moving thesaid stylus in a second direction substantially at right angles to thefirst movement and substantially proportional to the dynamic pressure sothat the stylus makes a record of the instantaneous values ofappliedaccelerations of air speeds.

2. An instrument for an aircraft comprising a chart, means responsive toaccelerations of the aircraft, means responsive to dynamic pressuresopposing the aircraft and means connected with the accelerationresponsive means and dynamic pressure responsive means for recording inone operation on said chart the relation of accelerations of theaircraft to the dynamic pressures opposing the aircraft.

3. The method of indicating during the flight of an airplane theapproach and existence of any flight condition characterized by certainpredetermined combinations of the variables of acceleration acting onthe airplane in a direction substantially perpendicular to the liftingsurfaces of the airplane and the dynamic pressure due to the velocity ofthe airplane through the air comprising, simultaneously measuring thevalues of such variables, and indicating the relationship between theactual value of one of said variables so measured and the value of suchvariable which in conjunction with the measured value of the othervariable will produce one of said predetermined combinations of thevariables of acceleration and dynamic pressure.

4. The method of indicating during the flight of an airplane theexistence of any flight condition characterized by a certainrelationship between the variables of acceleration of the airplane in adirection substantially perpendicular to the lifting surfaces of theairplane and the dynamic pressure due to the velocity of the airplanethrough the air as expressed by a curve showing for any given value ofone of said variables the value of the other variables which will reducein some structural member of the airplane a predetermined load for thatmember comprising, simultaneously measuring the values of both of suchvariables, and indicating the relationship between the actual value ofone of said variables so measured and that value of the same variablewhich in conjur :tion with the measured value of the other variable willproduce the predetermined load on such member.

5. The method or indicating during the flight of an airplane theapproach and existence of any flight condition characterized bycertainpredeterminedcombinations of the variables of acceleration acting on theairplane in a direction substantially perpendicular to the lifting sur-4 faces of the airplane and the dynamic pressure means responsive toaccelerations of the aircraft for actuating the record producing meansin one direction substantially proportional to the applied accelerationand a second means responsive to dynamic pressure for actuating therecord producing means in a direction substantially at right angles tothe first direction so that a record of the instantaneous values ofapplied accelerations against dynamic pressures is made on the chart.

.7. An instrument for an aircraft comprising a chart movably positionedin the instrument, and means for producing a record on said chart, saidrecord producing means including acceleration responsive means and meansresponsive to dynamic pressure whereby a composite record ofacceleration and variation in air speed is recorded on the chart.

8. An instrument for an aircraft comprising a chart, a stylus ,forrecording on said chart, a dynamic pressure cell, means connecting saidcell to the stylus for moving the stylus in certain directions over thechart, means responsive to changes in acceleration of the aircraft andmeans transmitting the movement of the acceleration responsive meanstothe stylus for moving the stylus over the chart in directions transverseto the movements caused by said pressure cell.

9. An instrument for an aircraft comprising a chart, a floating pivotstructure mountedin the instrument, a stylus forrecording on said. chartand having an arm pivotally secured to said structure, and accelerationresponsive means and dynamic pressure responsive means connected to saidpivot structure so as to control the movement of the stylus to recordinstantaneous values of applied accelerations against dynamic pressureson the chart.

10. An instrument for an aircraft comprising a chart, and means forproducing a composite record of acceleration and dynamic pressure .onthe chart, said means including acceleration responsiv means, meansresponsive to dynamic pressure and a floating pivot structure connectedto and controlled by said accelerationrcsponsive means and dynamicpressure'responsive means.

11. An instrument for an aircraft comprising a chart, and means forproducing a composite record of acceleration and dynamic pressure on thechart, said means including a stylus having an arm extending therefrom,acceleration responsive means, means responsive to dynamic pressure, anda floating pivot structure connected to the stylus arm, accelerationresponsive means

